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This study investigates the performance of a 4-MIX engine utilizing hydrogen combustion in pure oxygen, water injection, and the application of the early-intake valve closure (EIVC) Miller cycle. Transitioning from a standard petrol–oil mix to hydrogen fuel with pure oxygen combustion aims to reduce emissions. Performance comparisons between baseline and oxyhydrogen engines showed proportional growth in the energy input rate with increasing rotational speed. The oxyhydrogen engine exhibited smoother reductions in brake torque and thermal efficiency as rotational speed increased compared to the baseline, attributed to hydrogen's higher heating value. Water injection targeted cylinder and exhaust temperature reduction while maintaining a consistent injected mass. The results indicated a threshold of around 2.5 kg/h for the optimal water injection rate, beyond which positive effects on engine performance emerged. Investigation into the EIVC Miller cycle revealed improvements in brake torque, thermal efficiency, and brake specific fuel consumption as early-intake valve closure increased. Overall, the EIVC model exhibited superior energy efficiency, torque output, and thermal efficiency compared to alternative models, effectively addressing emissions and cylinder temperature concerns. [ABSTRACT FROM AUTHOR]

Nowadays, increasing the penetration of renewable heat technologies is an important approach to minimise global primary energy use and reduce CO2 emissions for a sustainable future. Thermoelectric heat pumps, which have some unique characteristics in comparison with conventional vapour compression heat pumps, can be integrated with solar thermal energy storage to form a promising renewable heat technology. However, currently, a reliable numerical model for TeHPs suitable for building energy simulation is lacking and the benefits achievable for a TeHP thanks to the integration with heat storage are unclear. To solve these issues, in this work, an experimental apparatus consisting of a water-to-air TeHP unit with a heat storage tank is modelled and tested for the first time, under the scenarios with thermal energy storage and without thermal energy storage, respectively. The results found that the developed numerical model could well predict the output performance of the TeHP unit, with deviations within 12%. Additionally, the output performance of the TeHP unit when combined with a heat storage tank is better than that of the TeHP unit without heat storage, in terms of the maximum temperature achieved in the testing box, the temperature response speed of the testing box, and the coefficient of performance (COP) of the TeHP unit. This work not only paves the way for the following building-integrated simulations of TeHP units, but also provides guidance for the design of the integrated systems that include TeHPs and thermal energy storage. [ABSTRACT FROM AUTHOR]

This paper investigated the effects of exhaust gas recirculation (EGR) on homogeneous charge compression ignition (HCCI) combustion in internal combustion engines. The exhaust valve closing (EVC) timings were scanned to obtain a set of baseline operating points for HCCI, and the coupling control of the internal and external EGR was explored. The results indicate that external EGR delays HCCI ignition timing and slows down the combustion speed. As the internal EGR rate increases, the maximum external EGR ratio that can be tolerated decreases. For HCCI detonation operating points with low internal EGR rates, the addition of up to 10% of external EGR can control the pressure rise rate peak to less than 10 bar/°CA, resulting in reduced fuel consumption and increased indicated mean effective pressure (IMEP). However, for HCCI operating points with high internal EGR rates, the effect of external EGR is mainly observed in the control of the pressure rise rate, with limited increase in IMEP. Additionally, an increasing external EGR rate leads to a significant decrease in nitrogen oxide (NOx) emissions, while carbon monoxide (CO) and hydrocarbon (HC) emissions slightly increase before engine misfire occurs. These findings suggest that the coupling control of internal and external EGR should be explored further, particularly in relation to reducing the negative valve overlap (NVO) angle and improving combustion efficiency. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the thermal and indoor environmental performance of an office building in the northeast of England. The building was built using natural stone and glass; internally the large floor plates are bordered and penetrated by open voids that ventilate the building and provide exceptional day lighting. A computational model for this building was set up using Design Builder software. The model is validated using on-site monitoring data and then it is used to predict and evaluate the performance of the building. It is found that the U-value of glass and natural stone is relatively high that caused high energy consumption. To achieve the performance recommended by passive house standard, two scenarios are proposed and simulated. It is found that when the window size is reduced and low U-value wall materials used, the energy consumption for heating can be reduced by 33.9% for Scenario 1 and 45.7% for Scenario 2 in a year. [ABSTRACT FROM AUTHOR]

Free-piston engine is a kind of linear internal combustion engine, and shows advantages on simple mechanical structure, low frictional losses, high thermal efficiency and operational flexibility. In this research, an experimental test rig of a dual-piston air-driven free-piston linear expander (FPLE) is established using the FPE concept. A linear generator is used to convert the mechanical work of the pistons into electricity during the expansion process. The piston dynamics, the output voltage of the generator, and the expander operation frequency, as well as the system energy conversion efficiency are identified. It is observed that the piston displacement profile is similar with a sinusoidal wave. The piston is found to run at relative high speed during the middle stroke, and peak velocity is usually achieved when the piston approaches the middle stroke. The output voltage of the generator is sensitive with the piston velocity. With higher driven pressure, the expander frequency is higher. The energy conversion efficiency increases with higher driven pressure and can reach up to 55% with a driven pressure of 3.75 bar. This research presents a fundamental analysis of a FPLE prototype, which can be used as a guidance for the future design of this FPLE type. [ABSTRACT FROM AUTHOR]

This paper presents an optimised resorption cogeneration using mass and heat recovery to improve the performance of a novel resorption cogeneration fist proposed by Wang et al. This system combines ammonia-resorption technology and expansion machine into one loop, which is able to generate refrigeration and electricity from low-grade heat sources such as solar energy and industrial waste heat. Two sets of resorption cycle are designed to overcome the intermittent performance of the chemisorption and produce continuous/simultaneous refrigeration and electricity. In this paper, twelve resorption working pairs of salt complex candidates are analysed by the first law analysis using Engineering Equation Solver (EES). The optimal resorption working pairs from the twelve candidates under the driven temperature from 100 °C to 300 °C are identified. By applying heat/mass recovery, the coefficient of performance (COP) improvement is increased by 38% when the high temperature salt (HTS) is NiCl 2 and by 35% when the HTS is MnCl 2 . On the other hand, the energy efficiency of electricity has also been improved from 8% to 12% with the help of heat/mass recovery. The second law analysis has also been applied to investigate the exergy utilisation and identify the key components/processes. The highest second law efficiency is achieved as high as 41% by the resorption working pair BaCl 2 –MnCl 2 under the heat source temperature at 110 °C. [ABSTRACT FROM AUTHOR]

Recent researches and studies demonstrate that the need for sustainable buildings which do less impact on the environment is rising in the worldwide [1,2] . Not only the energy generator from energy supply side needs to be considered to build a sustainable building, but also the novel construction methods and materials from demand side will contribute to the energy saving. The aim of this study is to carry out an investigation of a property's energy consumption from the view of passive energy saving, and then use the results to determine the best energy saving plan. A field audit and the Design Builder software simulation of a detached house were carried out during this study. The results indicate that the simulation energy consumption (9.66MWh) is matching well with the actual energy usage (9.76MWh) and the property consumes less energy than national average (16.90MWh). From the study, it is found that the annual total household energy consumption reduced for about 33% than traditional construction materials and technology by using passive energy saving methods. [ABSTRACT FROM AUTHOR]

Highlights: [•] An adsorption cogeneration was proposed and simulated for cooling and electricity. [•] A dynamic model was built and studied to demonstrate the variability of the system. [•] A dynamic model included the complex coupling of thermodynamic and chemical kinetic. [•] Mutual constrains between main components and optimisation methods were discussed. [•] The highest theoretical COP and exergy efficiency of cogeneration is 0.57 and 0.62. [ABSTRACT FROM AUTHOR]

In this paper, validated simulations using Ricardo WAVE have been performed to investigate the effect of the Miller cycle and low-carbon fuels on the performance (power, torque, BTE and BSFC) and emissions of a diesel engine. The results show that the increased Miller cycle effect (larger deviation of the advanced or retarded intake valve closing from the standard intake valve closing time) will decrease NOx, CO and HC emissions, and slightly improve brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) with slight loss in engine performance and increase in soot emissions. An engine running B0 (diesel with 0% Biodiesel in the blend) with a −18% Miller cycle effect has a reduction in NOx of 9% and CO of 4.3% with a decrease of 1.6% in power at the rated engine speed. Using low carbon fuels drastically reduces emissions with reduced BTE and increased BSFC. When used in conjunction, the Miller cycle and low-carbon fuels have an improved effect on both performance and emissions. The optimal results demonstrate that using B60 (60% Biodiesel in the blend) and a −8% Miller effect contributes to a 1.5% improvement in power, 1.2% in BTE, 13.3% in NOx, 38.5% in CO, 8.9% in HC, and 33.0% in soot at a cost of 6.0% increase in BSFC. The results show that it is an easy way to reduce NOx, CO, HC and soot emissions and increase the BTE of the engine by combining Miller cycle and low-carbon fuels. [ABSTRACT FROM AUTHOR]

Abstract: This study examined the performance and emission characteristics of a household size trigeneration based on a diesel engine generator fuelled with hydrogen comparing to that of single generation, cogeneration using ECLIPSE simulation software. In single generation simulation, the engine genset is used to produce electricity only and the heat from the engine is rejected to the atmosphere. In cogeneration and trigeneration, in addition to the electricity generated from the genset, the waste heat rejected from the hot exhaust gases and engine cooling system, is captured for domestic hot water supply using heat exchangers and hot water tank; and a part of the waste heat is used to drive absorption cooling in trigeneration. Comparisons have been made for the simulated results of these three modes of operation for hydrogen and diesel. The results prove that hydrogen is a potential energy vector in the future which is a key to meeting upcoming stringent greenhouse gases emissions. The study show that hydrogen has very good prospects to achieve a better or equal performance to conventional diesel fuel in terms of energetic performance, and a near zero carbon emission, depending on the life cycle analysis of the way the hydrogen is produced. The results also show enormous potential fuel savings and massive reductions in greenhouse gas emissions per unit of useful energy outputs with cogeneration and trigeneration compared with that of single generation. [Copyright &y& Elsevier]

Abstract: The performance and the efficiency of a trigeneration system fueling with pure diesel and with raw jatropha oil are investigated using the ECLIPSE software. The study is based on a diesel engine generating set. The genset is used for electrical power generation only, acting as a single generation. The trigeneration system consists of the genset, a waste heat recovery system and an absorption refrigerator. The genset is used to generate electricity; the waste heat system is used to collect the waste heat from the cooling system and the exhaust from the engine, to supply heating/hot water; and the absorption refrigerator is used to supply cooling/refrigeration, which is driven by the waste heat from the engine instead of electricity. A comparison of the thermal efficiencies and the CO2 emissions of trigeneration with single generation and cogeneration (combined heat and power — CHP) is carried out. The results from the study show that the thermal efficiency of trigeneration is higher than that of single generation; the CO2 emissions of trigeneration are lower than that of single generation. The results also show the performance differences between the trigeneration and single generation; and the differences between trigeneration and cogeneration. [Copyright &y& Elsevier]

There are few experimental reports combining hybrid energy storage and diesel engine generators as the power source of distributed power generation systems. In this article, a distributed power generation with energy storage system (DG-ES) which contains a diesel engine generator and an energy storage unit is set up and tested in the laboratory to satisfy the dynamic changing load. The hybrid energy storage system is composed of a lead-acid battery and a supercapacitor. The DG-ES supplied power to meet the domestic load demand successfully under different seasons. A simulation model of this system was also set up in MATLAB software used to guide to the experimental operation of this system. The simulation results has 2.69% and 2.35% error. The results of the experimental tests show the DG-ES can provide enough power to meet the dynamic loads of the selected house, especially at peak time in both winter and summer time. Computational simulation results show that the performance of DG-ES is improved by 3.61% in summer and 1.86% in winter when the system's operations are optimised. [ABSTRACT FROM AUTHOR]

Small-scale organic Rankine cycle (ORC) systems driven by solar energy are compared in this paper, which aims to explore the potential of power generation for domestic utilisation. A solar thermal collector was used as the heat source for a hot water storage tank. Thermal performance was then evaluated in terms of both the conventional ORC and an ORC using thermal driven pump (TDP). It is established that the solar ORC using TDP has a superior performance to the conventional ORC under most working conditions. Results demonstrate that power output of the ORC using TDP ranges from 72 W to 82 W with the increase of evaporating temperature, which shows an improvement of up to 3.3% at a 100 °C evaporating temperature when compared with the power output of the conventional ORC. Energy and exergy efficiencies of the ORC using TDP increase from 11.3% to 12.6% and from 45.8% to 51.3% when the evaporating temperature increases from 75 °C to 100 °C. The efficiency of the ORC using TDP is improved by up to 3.27%. Additionally, the exergy destruction using TDP can be reduced in the evaporator and condenser. The highest exergy efficiency in the evaporator is 96.9%, an improvement of 62% in comparison with that of the conventional ORC, i.e., 59.9%. Thus, the small-scale solar ORC system using TDP is more promising for household application. [ABSTRACT FROM AUTHOR]

Highlights • A holistic and comprehensive sustainability assessment model is proposed. • Three solar photovoltaic systems are assessed for their sustainability performance. • CdTe solar PV system performed the worst among the three systems. • Polycrystalline solar PV system is the most sustainable choice in all categories. Abstract This paper proposes a comprehensive sustainability assessment model incorporating (a) life cycle approach and sustainability theory. In the model, sustainability is assessed from three categories: techno-economic, environmental and social. A total of thirteen indicators were included in the proposed model, with five evaluating the techno-economic performance, six evaluating the environmental performance, and two examining the social impact. The effectiveness of this model is then demonstrated through its application to a case study of solar photovoltaic in the North East region of England. Three types of the most commonly deployed solar photovoltaic electricity generation systems are included in the case study: monocrystalline (s-Si), polycrystalline (p-Si) and Cadmium telluride (CdTe) thin film. The multi-silicon solar photovoltaic system is found to be the most sustainable option for its high performance in the techno-economic and environmental categories; the CdTe based system is the least-favoured option across all three categories; and the polycrystalline system has the best performance across all categories. Energy conversion efficiency appears to be one of the most influential factors for the solar photovoltaic system’s sustainability performance. Despite being the least costly system among the three, the CdTe system appears to be the least financially viable option mainly due to its low energy-conversion efficiency. This study estimates the environmental impact of selected technologies using the CML2001 method and then employs ReCiPe method to cross-validate the estimated results. Identical results were found for all indicators apart from eutrophication potential, due to the difference in impact quantification methods between CML and ReCiPe. [ABSTRACT FROM AUTHOR]

This study investigates the effects of carbon coated aluminum (Al@C) nanoparticles added to diesel-biodiesel blends as additives on engine performance and emissions. The Al@C nanoparticles are added into the diesel-biodiesel fuel in the mass fractions of 30 ppm under ultrasonic mixing. The experimental tests are conducted using a Cummins diesel engine. For comparison, three kinds of fuels including diesel-biodiesel blend (B10), B10 with 4% ethanol (B10E4), and B10 with 4% ethanol and 30-ppm nanoparticles (B10E4N30) are used for the tests under the European Stationary Cycle (ESC). The results show clearly that adding Al@C nanoparticles can reduce brake specific fuel consumption (BSFC) by 6% on average; along with a drop of 6% in NO X emission and CO emission is reduced by 19%, comparing with B10. However, the presence of ethanol in fuel blend increases THC emission. Nevertheless, addition of Al@C nanoparticles reduces THC emission by 14.5% compared with B10E4. The emission of particles number (PN) is increased by 2.2 times for B10E4N30 on average but is reduced by 11.8% for B10E4 (adding ethanol only) on the contrary, compared to B10. The studies on morphology and phase structure of nanoparticles after combustion indicate that Al@C nanoparticles have been transformed into alumina nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: An experimental study of the performance and emission characteristics of diesel engine using direct and indirect injection combustion systems are carried out on a same model of two diesel engines fuelled with diesel and the blend of diesel and Chinese pistache biodiesel. The results show that the NOx emissions from the indirect injection combustion system (ICS) fuelled with diesel are reduced by around two thirds, compared to that from direct injection combustion system (DCS). Smoke emissions from the engine using ICS are all significantly lower than that of DCS, reduced by 70% for diesel; by 50–60% for the blend. The brake thermal efficiencies (BTEs) reduced by 8–10%, compared to that of DCS; the fuel consumptions increased by around 7–9%. It is also found that carbon monoxide (CO) emissions are reduced when the engine run at engine high power outputs, so are the hydrocarbon (HC) emissions from ICS at the peak power outputs. It is found that, when fuelled with the blend, the effects of ICS to the performance and emissions of diesel engine are very similar to that of running with diesel. For ICS engine fuelled with diesel and the blend fuel, the BSFCs for the blend are around 5% higher; the BTEs are around 2–4% lower; the reductions of NOx from the blend fuel are 5.1–8.4% on average for the ICS; the reductions of smoke from the blend fuel are 26.8–31.7% on average for the ICS. CO emissions are around a half lower; and HC emissions are around one fifth lower, compared to that of fuelling with diesel. Comparing to that of DCS fuelled with diesel, using ICS fuelled with the blended fuel has much lower emissions. NOx emissions decreased by 65.6% and 66.1%; smoke emissions decreased by 75.7% and 80.2%; CO emissions decreased by 55.8% and 46.0%; HC emissions decreased by 24.9% and 18.9%; with the BSFCs around 14.6–14.9% higher and the BTEs around 9.7–10.0% lower. [Copyright &y& Elsevier]

This paper investigates the heat transfer characteristics of the external ventilated path of a compact, 6 kV, 4-pole, 2500 kW motor using flow-thermal coordination mechanism. A computational model is set up and validated by experimental test results. A series of simulation is performed. It is found that the deflection angle α and outlet angle β of the fan blades are the key parameters affecting the efficiency of the cooling effect of the fan. Optimal measures are adopted by changing the deflection angle and outlet angle of fan blades. External fan efficiency is improved from 28.80% to 29.96% and outlet flow is increased by 0.08 m 3 /s by optimizing the deflection angle α and outlet angle β. According to the optimization results of external fan, heat transfer characteristics and temperature distribution of the cooler is obtained by the fluid and temperature coupling field. The cooler is optimized by adjusting the height of the windshield, increasing the number of the windshield, changing the shape of inclined plate. It is found that the temperature of hyperthermal fluid of inner ventilated path is decreased from 75 °C to 53.7 °C; at the same time the temperature of cryogenic fluid of external ventilated path is increased from 23 °C to 49.4 °C. The outlet temperature of internal fluid of post-optimized cooler is dropped by 3 °C, and the external fluid temperature is increased by 2.5 °C. The performance of fan and the cooling effect is improved. The results from this study can provide an effective method for structural optimal design of compact high-voltage motors. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a novel resorption cycle driven by the low grade heat for the cogeneration of electricity and refrigeration, which is based on ammonia adsorption refrigeration technology. The presented cycle features a variable endothermic process which stands for higher adaptability if compared with the traditional Rankine cycle, very little or no ammonia liquid in the system which is a safety feature, solid adsorbents inside the beds, and simple structure for the fact of no rectifying equipment and circulation pumps required by the working fluids. This cycle can be utilised for the heat source with the temperature higher than 100°C, and it has an electricity generation exergy efficiency of up to 0.69 and a refrigeration coefficient of performance (COP) of up to 0.77. If compared with the Goswami cycle, which is established based on the absorption Kalina cycle for the cogeneration of electricity and refrigeration, the novel resorption cycle kept the merit of the high exergy efficiency for electricity generation, meanwhile, it overcame the limitation of the low refrigeration coefficient of performance (COP) of Goswami cycle, and improved the COP by 10 times. The optimum overall exergy efficiency is as high as 0.9, which is 40–60% improved compared with the Goswami cycle under the same working conditions. [Copyright &y& Elsevier]

Abstract: Thermal energy loss in the process industry is a significant issue due to the high temperatures and multiple heat intensive processes involved. High-grade thermal energy is typically recovered within processes. However, lower grade heat is often rejected to the environment. The benefits of capturing and utilising low grade thermal energy are highly dependent on the qualities and properties of the heat in the waste streams. The temperature of the low grade heat stream is the most important parameter, as the effective use of the residual heat or the efficiency of energy recovery from the low grade heat sources will mainly depend on the temperature difference between the source and a suitable sink, e.g. another process or space heating/cooling. In general, the temperatures of these waste heat sources are too low to produce electricity and direct heat use will depend on whether potential user can be found. This paper presents past and current drivers for heat recovery studies. High and low grade heat sources are defined according to the viability of recovery within the processes. Firstly, high grade heat capture within the processes is reviewed. Then, the focus is on the potential for low grade heat capture outside of the original plant. The paper addresses the potential for low grade heat recovery with regard to new incentives and technological advances. Finally, different aspects which influence the decision making for low grade heat recovery in the process industry are discussed. It is concluded that organisational, financial and economic barriers might be overcome and benefits from a holistic vision could be gained with stronger governmental policy and regulation incentives. [Copyright &y& Elsevier]